Comparative testing of the potency of different PPD preparations.

The potency of different PPD preparations, obtained from M. tuberculosis and M. bovis was investigated in the guinea-pig test. The groups of animals were immunized with dried mycobacterium powder (obtained from M. tuberculosis, M. bovis and M. tuberculosis + M. bovis), suspended in sterile liquid paraffin oil and with BCG vaccine. The potency tests were carried out according to the WHO requirements. Independently of the immunization method, a significantly greater potency of homologous versus heterologous PPD could not be demonstrated. The mixed PPD preparation (obtained from M. tuberculosis + M. bovis) was fractionated on SEPHAROSE 6 B and SEPHACRYL S 200 column. The potency of different fractions compared to the non-fractionated material was determined in the guinea-pig tests. The animals were immunized by dried mycobacterium powder (obtained from M. tuberculosis + M. bovis), suspended in sterile liquid paraffin oil. The IU content of fractions was calculated according to their protein N content, compared to the non-fractionated material. In these experimental conditions PPD fractions with significantly greater potency than the non-fractionated material could not be found. As a final conclusion we suggest that the desired improvement of tuberculosis diagnostics can be achieved not only by using PPDs derived from different mycobacteria but by further immunochemical purification of the tuberculin preparations and extensive testing of the purified materials in human beings as well.

Potency of PPD preparations derived from M. tuberculosis and M. bovis.

No significant difference was found between the biological activity of PPD-preparations derived from M. tuberculosis and M. bovis, although the latter was more potent. In potency tests performed in guinea-pigs, the use of difference mycobacteria as sensitizing agents had no influence on the result of the assay. We could not demonstrate a significantly greater potency of homologous versus heterologous PPD. Evaluation of the 95 p.c. fiducial limits established in the course of variance analysis suggested a greater reliability of reading at 48 than at 24 hrs after allergen application. It also seems possible that the results of the potency assays of PPDs derived from different mycobacterium strains are greatly influenced by the level of the working dilutions employed.

Biological standardization of potency testing of diphtheria-tetanus-pertussis vaccines.

Active protection tests were introduced for the potency testing of the toxoid components of the DTP vaccine. The standardization of these tests is described, with special attention on WHO requirements. A freeze-dried, adsorbed DTP vaccine was prepared for use under tropical or subtropical conditions. The potency testing of the components of this vaccine is presented in this paper.

Stability of cholera and typhoid vaccines.

Fluid plain and adsorbed and freeze-dried cholera and tyhpoid vaccines of different composition were examined for thermostability by potency testing (by active mouse protection tests) after exposure to 37 degrees C for 1, 2, 3, 4, 8 and 12 weeks. Loss of potency was evaluated by comparison with samples stored at 4 degrees C. The fluid plain cholera vaccine remained fully potent for 1--3 weeks, the adsorbed vaccine for at least 4 weeks. The fluid typhoid vaccines showed greater thermosensitivity than the fluid plain cholera vaccine. The freeze-dried cholera and typhoid vaccines were both very stable, retaining fully potency after at least 12 weeks' exposure to 37 degrees C. It should be emphasized that the above results apply exclusively to vaccines prepared by the methods used by the authors and formulated to identical compositions.

Stability of mammalian tuberculin PPD.

Six lots of PPD prepared in 1937 met the requirements when tested in guinea pig potency assay in 1974. Reading of the skin reactions at 48 hr gave more consistent results than the 24 hr reading. Data were evaluated by analysis of variance and by a quick method developed for the estimation of identity of the standard and the test preparation. Although less sensitive than the analysis of variance, the quick method has been found suitable for estimation of the potency of tuberculin preparations.

A quick method for the estimation of the potency of tuberculin purified protein derivative in guinea pig.

By the statiscal analysis of the data the linear regression equation and standard deviation of the dose response function of the Hungarian Reference Purified Protein Derivative of Tuberculin (HR--PPD) have been determined. From the values of reaction diameters of the HR-PPD and of their standard deviation a diagram was plotted that can be used to estimate the identity of test material by comparison with the reference preparation. The diagram meets the condition that the limits of the standard deviation of the reference and test materials together are wider than the predetermined limits of +/-20%. The inaccurate titrations can be detected with its help at once. Using the diagram, the potency of test material can be promptly estimated in the biological assay of tuberculin made in guinea pig.

Factors influencing the stability of acid-precipitated polyvalent Bordetella pertussis bulk suspensions.

According to the statistical analysis of the potency values of acid precipitated polyvalent bulk suspensions of Bordetella pertussis, the potency of suspensions decreased below 8 IU/30 IOU during storage for 5 to 9.8 years. The average annual decrease over a 13-year period was 2.03 IU/30 IOU. The periodicity in the decrease of potency values was assumed to be connected with changes in the quality of the casein hydrolysate ingredient of the medium. Periodic functions employed to approach potency values with limits of 1 SD falling within the range of 64--156% indicated that the potency decreased below 8 IU/30 IOU after 9 years.

Standardization of housedust allergen in human skin test trials.

Standardization was carried out by comparison of Bencard and our own ('Human') housedust allergens in human skin test trials. The dose response curves on hypersensitive patients were parallel, linear, and there was no difference between preparations according to the variance analysis. The relative potency was 1.33 compared to the Bencard allergen. 95% confidence limits were 0.29-2.37. The correlation coefficient evaluated from all data was 0.90. Our experience suggests that human skin test trials seem to be a simple and convenient method for the standardization of housedust allergens. According to the results of analysis of factorials, data suitable for standardization can be obtained if the area of both the wheal and flare as different parameters are recorded 10 and/or 20 minutes after the intradermal injections.